The present invention relates generally to a projection headlamp of the type in which light beams reflected by a substantially elliptical reflector are projected forward by a projection lens. More particularly, the invention relates to a projection headlamp for vehicles capable of selectively changing a beam distribution pattern from one pattern to another by tilting a shade.
Conventional headlamps of this type are disclosed in Unexamined Japanese Utility Model Application (OPI) No. Sho. 63-41801 and Unexamined Japanese Patent Application (OPI) No. Sho. 1-213901. The headlamp of the Utility Model Application is constructed as shown in FIG. 19. As shown, a light source 3 is positioned at the first focal point F1 of a reflector 2 shaped substantially elliptical, and a shade 4 is positioned at the second focal point F2. A projection lens 5 is located in front of the shade 4. In the headlamp thus constructed, for selectively changing a beam distribution pattern from one beam pattern to another, the shade 4 is turned about a horizontal support shaft O, to partially intercept light beams directed toward a projection lens 5. Reference numeral 1 designates a lamp body, and numeral 6, a front lens.
The headlamp of the Patent Application employs shade turning means different from that of the conventional apparatus, $Utility Model Application, but the headlamps are both based on the same idea that, to select the main beam distribution pattern or the sub-beam distribution pattern, the shade is turned.
The prior headlamp is capable of selecting one of only two patterns, the main beam distribution pattern and the sub-beam distribution pattern. In other words, it cannot select a beam distribution pattern, e.g., a medium beam distribution pattern of a middle state between the main beam and sub-beam distribution patterns. In a highway drive, as the running speed of the vehicle is higher, the beam distribution pattern of the headlamp, when it is closer to the main beam distribution pattern, will provide a better visual recognition of the driver, but will give a more intensive glare to the driver of the vehicles running in the opposite direction. In this case, it is very convenient if the medium beam distribution pattern can be used, which will not give a glare till the vehicles running in the opposite directions come near to each other within a preset distance. There is no prior art which can select any of other beam distribution patterns than the main beam distribution pattern and the sub-beam beam distribution pattern, in addition to the latter ones. In this respect, the market of this field demands the development of this type of headlamp.